Sealed packages are necessary to contain, protect, couple to optical fibers and electrically connect optoelectronic components. Optoelectronics packaging can be one of the most difficult and costly operations in optoelectronics manufacturing. Optoelectronic packages provide submicron alignment between optical elements, high-speed electrical connections, excellent heat dissipation, and high reliability. Providing such features results in optoelectronic packages that are larger, costlier and more difficult to manufacture than electronic packages. In addition, current designs of optoelectronic packages and associated fabrication processes are ill adapted for automation because today's high-performance butterfly packages are characterized by a large multiplicity of mechanical parts (submounts, brackets, ferrules, etc.), three-dimensional (3D) alignment requirements, and poor mechanical accessibility.
One type of package for an edge-coupled optoelectronic device includes a cover with a window, so that an optoelectronic device, such as a laser, may be coupled to external optics, such as a lens or an optical fiber. See, for example, U.S. Pat. No. 4,953,006 by Kovatz. Although this type of package can provide hermeticity and high-speed electrical connections, it does not provide for a way to mount and align collimation or coupling optics nor optical fibers.
U.S. Pat. No. 5,005,178 by Kluitmans and Tjassens and U.S. Pat. No. 5,227,646 by Shigeno also disclose packages for optical and optoelectronic components. Kluitmans et al. discuss a package for a laser diode coupled to an optical fiber. The package includes a conducting rod so that the laser may be used at high speed. Shigeno describes a heat sink for cooling an enclosed laser diode, where the laser diode is preferably coupled to an optical fiber. However, in both of the above patents, it is difficult to align the laser diode with the optical fiber when constructing the package. Both designs use numerous parts in complex three dimensional arrangements and are unsuitable for automated assembly. U.S. Pat. No. 5,628,196 by Farmer discloses a package including a heat sink for a semiconductor laser, but provides no efficient means for coupling the laser to other optics.
In most current types of packages, it can be difficult to align the laser diode with the optical fiber when constructing the package. The process of aligning an optical fiber to a laser diode and fixing it in place is known as fiber pigtailing. Current designs use numerous parts in complex three dimensional arrangements that can be unsuitable for automated assembly. Similarly, on the receive side of optical packages, it can be difficult to align the receiving component with the optical fiber.
The difficulty in alignment during fiber pigtailing is made more problematic where soldering is involved in the manufacturing of a package. The result of the soldering process causes a shift to occur in the structure being soldered due to shrinkage of the molten weld material while it is solidifying. Therefore, even though something is aligned prior to soldering, the result of the soldering process may cause such shifts to occur. Where micron accuracy is needed, these shifts affect the overall yield.
Typically, in prior optical alignment techniques, the optical fiber and flexure were soldered together or bonded together when they were placed inside the optical package. The optical fiber and flexure were then aligned at that time with components already in the optical package. Thus, the optical package was built up and the flexure, the optical fiber, the optical fiber in respect to the flexure, and one or more components inside the package that optically mate up to the combination of the fiber and flexure were all aligned at the same time.
Some aligning techniques can be used to reduce the effect of such post soldering shifting including pre-compensation for post soldering shifting, laser hammering, or “bending” of the parts after soldering. However, the overall yield can still be low even with these techniques because often too much correction and aligning of components has to be done.
While the invention is subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. The invention should be understood to not be limited to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.